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DOES PUBLIC OPINION INFLUENCE THESUPREME COURT? POSSIBLY YES
(BUT WE'RE NOT SURE WHY)
Lee Epstein*Andrew D. Martin*
INTRODUCTION
Using qualitative data and historical methods, Barry Friedman
as-serts with confidence that "we the people" influence the
decisions ofthe U.S. Supreme Court.' Using quantitative data and
statistical me-thods, political scientists are not so sure. Despite
their best efforts tovalidate basic claims about the effect of
public opinion on the Court,the evidence remains mixed at
best.2
We enter this dialogue but in a voice distinct from existing
politi-cal science work. Rather than explore the relationship
between thepublic and the Court on a term-by-term basis, we analyze
it at the lev-el of the case. This allows us to exploit more
nuanced public opiniondata, as well as to attend to the many other
case-level factors that mayinfluence the Court's decisions.
Based on our analysis, we are prepared to say that
ProfessorFriedman is on to something. When the "mood of the public"
is lib-eral (conservative), the Court is significantly more likely
to issue lib-eral (conservative) decisions. But why is anyone's
guess. Professor
* Lee Epstein (http://epstein.law.northwestern.edu/) is the
Henry Wade Rogers Professorat Northwestern.
* Andrew D. Martin (http://adm.wustl.edu/) is Chair of the
Political Science Departmentand Professor of Law and Political
Science at Washington University in St. Louis. We aregrateful to
Barry Friedman, Linda Greenhouse, and other participants at the
2010 Journalof Constitutional Law's Symposium for their helpful
comments. We also thank Jeffrey A.Segal and Richard A. Posner for
their insights, the National Science Foundation for re-search
support, and Jeremy Caddel and Jee Seon Jeon for research
assistance. Theproject's website houses a full replication archive:
http://epstein.law.northwestern.edu/research/PublicOpinion.html.
1 The full title of Professor Friedman's book tells the story.
BARRYFRIEDMAN, THE WILL OFTHE PEOPLE: How PUBLIC OPINION HAS
INFLUENCED THE SUPREME COURT AND SHAPEDTHE MEANING OF THE
CONSTITUTION 14 (2009) (stating that the decisions of the
SupremeCourt on contentious issues align with popular approval and
public understanding of theConstitution).
2 See infra Part II.
263
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JOURNAL OF CONSTITUTIONAL LAW
Friedman posits that the Justices will bend to the will of the
peoplebecause the Court requires public support to remain an
efficaciousbranch of government. Our analysis could be read to
support thisview, but it is equally consistent with another
mechanism: that "thepeople" include the Justices. On this account,
the Justices do not re-spond to public opinion directly, but rather
respond to the sameevents or forces that affect the opinion of
other members of the pub-lic.3 Or, as Cardozo once stated, "[t]he
great tides and currentswhich engulf the rest of men do not turn
aside in their course andpass the judges by."4
Our study proceeds as follows. In Part II, we briefly review the
ex-tant literature, emphasizing the similar methodology it invokes
butthe varying conclusions it reaches. Parts III and IV describe
our me-thods and findings. We end, in Part V, with the implications
of ourstatistical work for Professor Friedman's claims, as well as
for futureresearch assessing the Court's response to public
opinion.
II. THE EXISTING LITERATURE
Professor Friedman's book is only the last in a long and
distin-guished line of research evaluating the link between the
public andthe courts. Much, perhaps most, of the work in the social
scienceshas explored the flipside of Professor Friedman's interest:
the extentto which Court decisions affect (or "move") public
opinion.5 But
3 The debate between these two accounts has a long history in
the political science litera-ture. Compare Beverly B. Cook, Public
Opinion and Iederal judicial Policy, 21 AM.J. Pot. Sa.567, 574
(1977) (showing that federal judges were more lenient with Vietnam
WMar draftoffenders as public opinion toward the war grew
increasingly negative), with Herbert M.Kritzer, Federal judges and
Their Political Environments: The Influence of Public Opinion,
23AM.J. POL. Scl. 194, 195-98 (1979) (showing that changes in
severity of sentencing didnot move in the same way as changes in
public opinion, possibly reflecting "the judges'own doubts about
the war" rather than a direct response to public opinion). See
generally
JEFFREY A. SEGAL & HAROLD J. SPAETH, THE SUPREME COURT ANI)
THE ATTITUDINALMODEL REVISITED 424-25 (2002) (explaining that while
it is unsurprising that SupremeCourt decisions generally correspond
with public opinion, it is difficult to determinewhether public
opinion directly influences the Court).
4 BENJAMIN N. CARDOZO, THE NATURE OF THEJUDICIAL PROCESS 168
(1921).5 The classic work is Charles H. Franklin & Liane C.
Kosaki, Republican Schoolmaster: The
U.S. Supreme Court, Public Opinion, and Abortion, 83 AM. PoL.
ScI. REv. 751, 768 (1989)(finding that the Court's decisions have
an impact on the public, but that the impact ma-nifests itself as
both increased support and increased opposition for the position
taken bythe Court's majority). For recent research, see, e.g.,
Brandon L. Bartels & Diana C. Mutz,Explaining Processes of
Institutional Opinion Leadership, 71 J. Pol.. 249, 259 (2009),
reportingexperimental evidence that an endorsement from the Court
affected respondents' opin-ions about particular public policy
issues; Mark D. Ramirez, Procedural Perceptions and Sup-port for
the U.S. Supreme Cout, 29 Pol.. PSYCHOL. 675, 676 (2008), arguing
that positive me-
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WE'RE NOT SURE WHY
there is no shortage of quantitative (and multivariate) work
address-ing directly the question of whether the public influences
the Court.Rather than waste space with lengthy descriptions of each
paper, wesummarize the key results in Table 1. We limit our list to
studies ofthe U.S. Supreme Court, the focus of Professor Friedman's
book.6
TABLE 1
SUMMARY OF NOTABLE MULTIVARIATE STUDIES ON THE EFFECT OFPUBLIC
OPINION ON THE DECISIONS OF THE SUPREME COURT OR
INDIVIDUALJUSTICES
Author (Year) Description of Methods and Key Findings
Examines the number of federal laws struck down
by the Court each term; finds that as public support for
Clark (2009)' the Supreme Court declines, the Court strikes
down
fewer laws.
dia coverage increases support for the Court; James W.
Stoutenborough, and Donald P.Haider-Markel & Mahalley D. Allen,
Reassessing the Impact of Supreme Court Decisions on Pub-
lic Opinion: Gay Civil Rights Cases, 59 POL. RES. Q. 419, 430
(2006), asserting that theCourt is able to legitimate controversial
policies. See aLso ValerieJ. Hoekstra, The SupremeCourt and Local
Public Opinion, 94 AM. POL. SCI. REV. 89, 91, 97 (2000) (relaying
the abilityof particular Court decisions to affect overall
evaluations of the Court in the geographicareas that gave rise to
the case).
6 Studies of other federal judges include Cook, supra note 3, at
574; Kritzer, supra note 3, at195-98. There are also studies of
state courtjudges. These are more uniform in their re-sults,
tending to confirm the obvious: that (elected) state court judges
must considertheir constituents' preferences to keep theirjobs.
See, e.g., Steven P. Croley, The Majori-tarian Difficulty: Elective
judiciaries and the Rule of Law, 62 U. CHI. L. REv. 689, 696-97,
788
(1995) (criticizing elective judiciaries because they respond to
majoritarian political pres-sures); James H. Kuklinski & John
E. Stanga, Political Participation and Government Respon-siveness:
The Behavior of California Superior Courts, 73 AM. Pot. SCI. REV.
1090, 1093 (1979)(explaining findings that California superior
courts less in line with public opinionshowed adjustments in their
decisions); Alexander Tabarrok & Eric Helland, Court Poli-tics:
The Political Economy of Tort Awards, 42 J.L. & ECON. 157, 187
(1999) (indicating thatelected judges rule according to popular
views because they wish to be re-elected). Fi-nally, a growing
number of scholars are exploring the relationship between public
senti-ment and judicial decisions in courts outside the United
States. Along these lines, wecommend JEFFREY K. STATON, JUDICIAL
POWER AND STRATEGIC COMMUNICATION INMEXICO 3-4 (2010). Staton
documents the Mexican Supreme Court's "coordinated andaggressive"
public relations campaign to create public support. He also shows
that courtsthroughout the world publicize their decisions, issue
press releases, and maintain websitesdescribing their procedures
and publishing their cases and biographies of their members.
7 Tom S. Clark, The Separation of Powers, Court Curbing, and
judicial Legitimacy, 53 AM.J. POL.Sc. 971, 985 (2009).
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JOURNAL OF CONSTITUTIONAL LAW
Giles et al. (2008)8
McGuire & Stim-son (2004)'
Flemming &Wood (1997)'o
Mishler & Shee-han (1996) "
Stimson et al.(1995) 1
Link (1995) 4
Explores the percentage of liberal votes cast by eachJustice
each term; finds that public opinion exerts onlya small effect and
that it operates on "as few as 20%" oftheJustices serving between
1956 and 1999.
Analyzes the percentage of liberal decisions eachterm in cases
in which the Court reverses the court be-low; shows that the
public's mood affects the percent-age even after controlling for
ideology.
Analyzes the percentage of liberal votes cast by eachJustice
each term; shows that the Court's compositionaccounts for most of
the variation, but that the public'smood also exerts a small
(though significant and quick)effect on most Justices in the
majority of legal areas un-der analysis.
Considers the percentage of liberal votes cast byeach Justice
each term; finds that some moderate Jus-tices respond to the public
mood and concludes that it"shapes the subjective norms of
individual justices the-reby potentially influencing their
decisions.""
Analyzes the ideological direction of decisions eachterm;
unearths some responsiveness to the mood of thepublic, but the
effect nearly disappears when control-ling for the Court's
composition.
Examines the percentage of liberal decisions each
8 Micheal W. Giles, Bethany Blackstone & Richard L.
Vining,Jr., The Supreme Court in Ameri-can Democracy: Unraveling
the Linkages Between Public Opinion and judicial Decision
Making,70J. POL. 293, 296, 303 (2008).
9 Kevin T. McGuire & James A. Stimson, The Least Dangerous
Branch Revisited: New Evidenceon Supreme Court Responsiveness to
Public Preferences, 66J. POL. 1018, 1033 (2004).
10 Roy B. Flemming & B. Dan Wood, The Public and the Supreme
Court: IndividualJustice Re-sponsiveness to American Policy Moods,
41 AM.J. POL. SCI. 468, 474, 482 (1997).
11 William Mishler & Reginald S. Sheehan, Public Opinion,
the Attitudinal Model, and SupremeCourt Decision Making: A
Micro-Analytic Perspective, 58J. PoL. 169, 180 (1996).
12 Id. at 174.
13 James A. Stimson, Michael B. MacKuen & Robert S. Erikson,
Dynamic Representation, 89AM. POL. Sci. REV. 543, 552, 556
(1995).
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WE'RE NOT SURE WHY
Norpoth & Segal(1994)"
Mishler &Sheehan (1993)"
term in criminal procedure and race cases; finds thatthe
public's mood, to greater and lesser extents (andwith some lags),
has a direct effect on Court decisions.
Reexamines Mishler & Sheehan's 1993 study; findsthat any
change in the direction of the Court's deci-sions was due to an
"indirect model" of public influ-ence in which "popularly elected
presidents, throughnew appointments, affect the ideological
compositionof the Court."'
Explores the percentage of liberal decisions eachterm; finds
that (lagged) public mood influencesCourt's decisions both
indirectly (through compositionchanges) and directly; claims that
the Justices "arebroadly aware of fundamental trends in the
ideologicaltenor of public opinion, and . . . at least some
justices,consciously or not, may adjust their decisions at
themargins to accommodate such fundamental trends."
Two features of the studies in Table 1 stand out: their
commonmethodology and their mixed findings. Both deserve some
elabora-tion.
A. Common Methods
As even a cursory glance at Table 1 reveals, the studies tend to
fol-low the same methodological approach to answer the question
ofwhether public opinion influences the Court. They begin by
calculat-ing the percentage of liberal decisions (or votes) that
the Court (anindividual Justice) reaches each term-or, in the
jargon of social sci-ence, by aggregating decisions (votes) on a
term-by-term basis. Fig-ure 1 provides an example.
14 Michael W. Link, Tracking Public Mood in the Supreme Court:
Cross-Time Analyses of CriminalProcedure and Civil Rights Cases, 48
POL. RES. Q. 61, 67, 75 (1995).
15 Helmut Norpoth &Jeffrey A. Segal, Comment, Popular
Influence on Supreme Court Decisions,88 AM. POL. Sci. REv. 711, 711
(1994).
16 Id.17 William Mishler & Reginald S. Sheehan, The Supreme
Court as a Countermajoritarian Institu-
tion? The Impact of Public Opinion on Supreme Court Decisions,
87 AM. POL. SCI. REV. 87, 90,96 (1993).
18 Id. at 89.
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JOURNAL OF CONSTITUTIONAL IAW V
FIGURE 1. PERCENTAGE OF LIBERAL DECISIONS, 1953-2008 TERMS
80 -
70 -
.60
Sso -
40 -
30 -I I I II
1960 1970 1988 1990 2000 2010
Term
Because almost all the authors use the U.S. Supreme Court
Data-base to categorize decisions as liberal or conservative (as do
we inFigure 1), their definitions of ideology do not vary much.
Where dif-ferences emerge are in the types of cases they include in
their study.For example, some studies analyze only a few areas of
the law;'9 onefocuses on reversals; 0 and another separates the
cases into "salient"and "non-salient" categories.2 ' Figure 1 is a
generic depiction of thepercentage, using all cases decided between
the 1953-2008 terms."(As an aside, readers should take care in
interpreting Figure 1 or anyother display based on "percent
liberalism" because the types of casesthe Justices agree to hear
and decide in a given term will affect thepercentage.)
19 See, e.g., Link, supra note 14, at 67 (examining only
criminal procedure and civil rightscases). Others analyze
separately particular areas of the law or control for areas in
theanalysis. See, e.g., Flemming & wood, supra note 10, at
485-92 (evaluating whether spe-cific issue areas impacted judicial
responsiveness to public opinion); McGuire & Stimson,supra note
9, at 1025 (reflecting case outcome types for distinct issue
areas).
20 McGuire & Stimson, supra note 9, at 1019.21 Giles,
Blackstone & Vining, supra note 8, at 296.22 The percentage was
calculated using the U.S. Supreme Court Database, THE SUPREME
COURT DATABASE, http://supremecourtdatabase.org (last visited
Oct. 7, 2010) (cases or-ganized by citation), and orally argued
cases (decisionType = I or 6 or 7) in which the di-rection of the
decision is liberal or conservative (i.e., we omit the 60 cases
coded as "un-specifiable").
268 [Vol. 13:2
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WE'RE NOT SURE WHY
The percentage of liberal decisions (votes) per term is the
de-pendent variable in the studies (i.e., what the authors are
trying toexplain). The key independent variable is, of course,
public opinion.In other words, the authors are interested in
determining whether amore liberal public leads the Court (or the
individual Justices) toproduce more liberal decisions (votes) each
term, all else beingequal. To measure public opinion, the studies
typically rely on Stim-son's indicator of "public mood."2 3
Computed by analyzing survey re-sponses to a range of questions
with a sophisticated dynamic factoranalysis model, the indicator is
a single number summarizing themood of the public along a
liberal-conservative dimension. AlthoughStimson calculates his
measure on a quarterly basis, the articles inTable 1 use an annual
indicator of mood because their dependentvariable (percentage
liberalism) is also aggregated (though usually tothe term rather
than the year). Figure 2 displays this annual version.
FIGURE 2. STIMSON'S ANNUAL MEASURE OF THE "PUBLIC MOOD,"
1953-2008
70 -
E 65 -
u60 -
~55a s
E~ 50
45I I I I I II
1950 1960 1970 1980 1990 2000 2010
Year
23 JAMES A. STIMsON, PUBLIC OPINION IN AMERICA: MOODS, CYCLES,
AND SWINGS (2d ed.
1999). Updated at James A. Stimson, Time Series, UNIV. OF N.C.
AT CHAPEL HILL,http://www.unc.edu/-jstimson/time.html.
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JOURNAL OF CONSTITUTIONAL LAW
B. Mixed Findings
The final step in most of the studies in Table 1 is to
analyzewhether the annual public mood measure explains term-by-term
vari-ation in the Court's (Justices') liberal decisions (votes),
while control-ling for other factors that also might affect the
percentage of liberaldecisions (votes) each term. These other
factors almost always in-clude a measure of the Court's ideology
but otherwise tend to varyfrom study to study.24
Also varying from study to study are the results, though perhaps
itis worth starting with a common finding: virtually all the
studiesdemonstrate an indirect effect of public opinion via the
appointmentsprocess. That is, they tend to show that changes in the
Court's com-position can lead to a higher or lower percentage of
liberal decisionseach term. Political scientists deem this
"indirect" because the publicdoes not directly affect the
percentage of liberal decisions; its rolecomes in electing the
President and the Senate, who appoint andconfirm Justices
reflecting the public's preferences." Accordingly,"the ideological
orientation of the Court generally corresponds to theattitudes of
the electorate and the ruling regime.
The more controversial matter is whether the public directly
influ-ences Court decisions (as Friedman claims). The answers from
theexisting literature, as Table 1 suggests, run the gamut. Perhaps
thestrongest supporters of a direct, causal link between public
mood andCourt decisions, McGuire and Stimson, are as unequivocal as
Fried-man: "[P]ublic opinion is a powerful influence on the
decisions ofthe Supreme Court.... [The evidence shows that] a
system of popu-lar representation is alive and well in the Supreme
Court."2 In direct
juxtaposition comes Norpoth and Segal's famous reanalysis of
Mish-ler & Sheehan's 1993 study, in which they declare that
"contrary to
24 E.g., Flemming & Wood, supra note 10, at 468 (controlling
for different areas of the law);Giles, Blackstone & Vining,
supra note 8, at 296 (distinguishing salient and non-salientcases);
Link, supra note 14, at 69-70 (controlling for the preferences of
Congress and thePresident).
25 justice Antonin Scalia put it this way: "Ultimately, the
[Jiustices of the Court are takenfrom the society, ... and however
impartial they may try to be, they are going to bringwith them
those societ[al] attitudes." DAVID M. O'BRIEN, STORM CENTER: THE
SUPREMECOURT IN AMERICAN POLITIcs 343 (5th ed. 2000) (alteration in
original).
26 McGuire & Stimson, supra note 9, at 1020; see alto Robert
A. Dahl, Decivion-Making in aDemocracy: The Supreme Court as a
National Policy-Maker, 6J. PUB. L. 279, 293 (1957) (argu-ing that
the Supreme Court supports the major policies of the dominant
political powerbecause doing otherwise risks undermining its own
legitimacy if its rulings are not en-forced).
27 McGuire & Stimson, supra note 9, at 1033.
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WE'RE NOT SURE WHY
Mishler and Sheehan, [we find] no evidence for a direct path of
in-fluence from public opinion to Court decisions.",2 Charting a
moremoderate course are those scholars who identify some "direct"
butrelatively small effect. Stimson et al., fall into this
category:
Norpoth and Segal (1994) argue that the role of public opinion
onCourt decisions is wholly indirect through the
election-nomination-confirmation process. Mishler and Sheehan
(1993, 1994) claim a directpublic opinion influence. Our results,
with similar data but quite differ-ent model specification, leave
us in the middle of this debate. We believethere is a trace of
influence for both processes, but our results are tooweak to leave
us confident about the matter.
III. OUR STUDY
Although the studies listed in Table 1 are thoroughly
professionalefforts, published in top disciplinary journals,
features of their re-search design raise some red flags. Of
particular concern is that theycannot incorporate controls at the
case level because they aggregateby term. To provide but one
example: we know that the Justicestend to reverse the decisions of
the court below (usually a U.S. courtof appeals) .3o To account for
this tendency, researchers modeling theideological direction of the
Court's decisions (liberal or conservative)almost always
incorporate a variable encoding the direction of thelower court's
decision (liberal or conservative) . The idea is thateven a very
liberal (conservative) Supreme Court would be inclinedto reverse a
liberal (conservative) lower court decision given the ma-
jority's general propensity to reverse.It is easy to add this
variable if the study models decisions on a
case-by-case basis; it is impossible to do so if the study
models deci-sions on a term-by-term basis-as the existing public
opinion researchdoes-without running the risk of ecological
fallacy. The same holdsfor many other covariates of Court
decisions. Although some are an-nual (such as the ideology of the
median Justice), others are not, in-cluding the issue area and the
parties. Aggregating by term is not
28 Norpoth & Segal, supra note 15, at 711.29 Stimson,
MacKuen & Erikson, supra note 13, at 556.30 Between the 1953
and 2008 terms, the Court ruled for the petitioner in 64% of the
6286
orally argued cases in which the Supreme Court Database
specifies the direction of thedecision and a winning party. THE
SUPREME COURT DATABASE, supra note 22.
31 See, e.g., SEGAL & SPAETH, supra note 3; Lee Epstein et
al., Circuit Effects: How the Norm ofFederal judicial Expeience
Biases the Supreme Court, 157 U. PA. L. REV. 833, 872 (2009)
("con-trolling for the ideological direction of the lower court's
decision" in an analysis of the ef-fects ofJustices' circuit court
experience).
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JOURNAL OF CONSTITUTIONAL LAW
even an especially good strategy for considering the effect of
the pub-lic's mood on the Court because it fails to exploit
Stimson's quarterlydata.
For these reasons, our analysis of Friedman's thesis proceeds
atthe case level. The dependent variable is the ideological
direction ofeach decision in all orally argued cases between 1958
and 2008"-and not the percentage liberal each term. That is, we
intend to studythe decisions in 5,675 cases, rather than a single
percentage in 50terms.
By "ideological direction," we mean the direction of the
decision(liberal or conservative), as coded by the U.S. Supreme
Court Data-
33base, the same source most of the other public opinion studies
use.The database's classifications generally comport with
conventionalunderstandings. "Liberal" decisions are those in favor
of defendantsin criminal cases; of women and minorities in civil
rights cases; of in-dividuals against the government in First
Amendment, privacy, anddue process cases; of unions over
individuals and individuals overbusinesses in labor cases; and of
the government over businesses incases involving economic
regulation. "Conservative" decisions are thereverse. Table 2
provides basic summary information about this vari-able (and all
others in our analysis).
TABLE 2
Summary Statistics (N=5675)Variable Description Mean
I (Std. Dev.)Dependent Variable
Whether the Court reached a lib- 0.501Direction of Decision eral
(=1) or conservative (0.500)
(=O) decisionKey IndependentVariable
Stimson's quarterly measure of 61-0624Public Mood public mood
(the higher the score, (4.628)
the more liberal the public)
32 Quarterly public mood data begin with the fourth quarter of
1958 (covering all but twocases in the 1958 term) through the
fourth quarter of 2008 (covering only four cases ofthe 2008
term).
33 THE SUPREME COURT DATABASE, supra note 22.34 The minimum is
51.363; the maximum is 74.18.
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WE'RE NOT SURE WHY
Control Variables
Direction of the LowerCourt Decision
Ideology of the Su-preme Court
U.S. Liberal Party
U.S. Conservative Party
Civil Liberties
Economics
Judicial Power
Federalism
Ideology of the
Whether the court whose decisionthe Supreme Court
reviewedreached a liberal (=1) or conserva-tive (=0) decision
Martin & Quinn's estimate of theideology of the median
justice (thehigher the score, the more conser-vative the
median)
Whether the United States (or anagency), as petitioner or
respon-dent, argued for a liberal decision(=1) or not (=0)
Whether the United States (or anagency), as petitioner or
respon-dent, argued for a conservative de-cision (=1) or not
(=0)
Civil Liberties case (=1) or not
(=0)m
Economics case (=1) or not (=0)
Judicial power case (=1) or not (=0)
Federalism case (=1) or not (=0)
Poole's Common Space score (the
35 The minimum is -.85; the maximum is 1.027.36 The Civil
Liberties category includes Criminal Procedure, Civil Rights, First
Amendment,
Due Process, Privacy, and Attorneys (i.e., "issueArea" = 1, 2,
3, 4, 5, 6) in the U.S. Su-preme Court Database. THE SUPREME COURT
DATABASE, supra note 22.
37 The Economics category includes Unions, Economic Activity,
and Taxation (i.e., "is-sueArea" = 7, 8, 12) in the U.S. Supreme
Court Database. THE SUPREME COURTDATABASE, supra note 22.
0.463(0.499)
0.364 35(0.495)
0.065(0.247)
0.134(0.340)
0.549(0.498)
0.275(0.446)
0.129(0.335)
0.048(0.214)
-0.21 1
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JOURNAL OF CONSTITUTIONAL LAW
President higher the score, the more conser- (0.519)vative the
President)
Poole's Common Space score (the
higher the score, the more conser- 0.0573"vative the House)
(0.114)
Poole's Common Space score (the 0.06940Ideology of the Senate
higher the score, the more conser- (0.106)
vative the Senate)
The independent variable of primary interest is Stimson's
quar-terly public mood measure. Because lower scores are more
conserva-tive, we expect this variable to be positively related to
the direction ofthe decision. In other words, if Friedman is right
and public opinioninfluences the Court, then the more liberal the
public mood, thehigher the likelihood of a liberal decision.
Finally, we include in the model a host of variables that might
alsoaffect the Court's decision (see Table 2). Seven are case-level
vari-ables: the direction of the lower court's decision, the side
repre-sented by the U.S. government (if it was a party to the suit,
liberal orconservative), and four issue dummies ("Federalism" is
the omittedcategory in the model). Given the Court's tendency to
reverse (andour coding of the relevant variables), we expect the
direction of thelower court decision to be negatively related to
the Court's decision.As for the U.S. government, the existing
literature suggests that theside it represents will prevail more
often than not.4' If so, "U.S. Lib-
38 The minimum is -.724; the maximum is .503.39 The minimum is
-.226; the maximum is.194.40 The minimum is -.199; the maximum is
.183.41 See, e.g., REBECCA MAE SALOKAR, THE SOLICITOR GENERAL: THE
POLITICS OF LAW 145
(1992) ("[B]etween 1959 and 1986.... [tlhe party that the
government supported withan amicus brief won 71.9 percent of the
time."); JEFF YATES, POPULAR JUSTICE:PRESIDENTIAL PRESTIGE AND
EXECUTIVE SUCCESS IN THE SUPREME COURT 96 (John Ken-neth White ed.,
2002) (noting the "overwhelmingly successful record" the solicitor
gen-eral has before the Court); see also RICHARD L. PACEI.E,JR.,
BETWEEN LAW AND POLITICS:
THE SOLICITOR GENERAL AND THE STRUCTURING OF RACE, GENDER, AND
REPRODUCTIVE
RIGHTS LITIGATION 5 (James P. Pfiffner ed., 1st ed. 2003) ("The
Court ... grants a higherpercentage of the solicitor general's
petitions and the government is more successful onthe merits than
any other litigant."); ROBERT SCIGUANO, THE SUPREME COURT AND
THE
PRESIDENCY 177 (Samuel Krislov ed., 1971) ("Throughout its
history the United States haswon most of its cases in the Supreme
Court."); Tracey E. George & Lee Epstein, On theNature of
Supreme Court Decision Making, 86 AM. Po.. Sa. REV. 323, 325 (1992)
("[Wie haveseveral reasons to suspect that Congress and the
[P]resident affect Supreme Court deci-sion making . . . .");
Jeffrey A. Segal & Cheryl Reedy, The Supreme Court and Sex
Discimina-
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WE'RE NOT SURE WHY
eral Party" should be positively signed; "U.S. Conservative
Party"should be negatively signed.
This leaves the four term-level covariates, all of which attempt
toassess the ideology of the various branches of government. For
theU.S. House of Representatives, the U.S. Senate and the U.S.
Presi-dent, we use Poole's Common Space scores. These reflect roll
callvotes in each House or, in the case of the President, his
position onbills before Congress.
We measure the Court's ideology using Martin and Quinn's
idealpoint estimate of the median Justice each term. The Martin
andQuinn measure is also based on votes-all those cast by the
Justices innon-unanimous cases. Table 2 supplies summary statistics
on all fourmeasures of ideology; Figure 3 depicts them over
time.
FIGURE 3. IDEOLOGY OF THE THREE BRANCHES OF GOVERNMENT
3a. The Senate, House, and President
- Senate MedianHouse Median
- Presidert. 0.5
E0
0.0
0
-0.5
I I I I II
1960 1970 1980 1990 2000 2010Year
tion: The Role of the Solicitor General, 41 POL. RES. Q. 553,
555-56 (1988) ("[T]he SupremeCourt is responsive to the executive
branch of government through its support for the so-licitor
general.").
42 VOTEVIEW.COM, http://voteview.com/ (last visited Oct. 7,
2010); see also KEITH T. POOLE& HOWARD ROSENTHAL, CONGRESS: A
POLITIcAL-ECONOMIC HISTORY OF ROLL CALLVOTING 7 (1997) (analyzing
the dynamics of roll call voting using a
liberal/conservativestructure).
43 MARTIN-QUINN SCOREs, http://mqscores.wustl.edu/ (last visited
Sep. 22, 2010); see An-drew D. Martin & Kevin M. Quinn, Dynamic
Ideal Point Estimation via Markov Chain MonteCarlo for the U.S.
Supreme Court, 1953-1999, 10 POL. ANALYSIS 134, 152 (2002)
(investigat-ing judicial preferences and finding that ideal points
of many justices change over time).
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3b. The Court
1960 1970 1980Year
1990 2000 2010
Under Poole's and Martin and Quinn's coding schemes, the
lowerthe ideology score, the more liberal the branch. Hence, if
these vari-ables affect the Court's decision, we expect negatively
signed coeffi-cients (i.e., the lower the score, the higher the
likelihood of a liberaldecision).
IV. RESULTS
To assess the effect of the public's mood on the ideological
directionof the Court's decision, we use logistic regression (with
various ro-bustness checks)." Table 3 displays the results. Note
that we clusterthe observations by term, which helps account for
any term-to-termcorrelations in the data (and results in higher
standard errors).
1.0
0.5 -
0 .
- 0.5 -
0
o0.0-E
E -
-1.0 -
44 For example, we reestimated the model using a random effects
logistic regression. Theresults are virtually identical to those
displayed in Table 3. Most importantly, the coeffi-cient on Public
Mood (Quarterly) remains statistically significant (.023, with a
standard errorof .007).
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TABLE 3 RESULTS OF REGRESSING THE DIRECTION OF THE
COURT'SDECISION (1=LIBERAL; 0=CONSERVATIVE) ON THE PUBLIC MOOD
AND
OTHER COVARIATES
Variable Coefficient (Standard Er-
I ror)Public Mood (Quarterly) 7 0.023 (0.008)Direction of the
Lower Court Decision -1.041 (0.070)Ideology of the Supreme Court
-0.547 (0.049)U.S. Liberal Party 0.316 (0.131)U.S. Conservative
Party -0.757 (0.095)Civil Liberties -0.287 (0.134)Economics -0.033
(0.135)Judicial Power -1.015 (0.148)Ideology of the President 0.017
(0.056)Ideology of the House -0.140 (0.331)Ideology of the Senate
0.283 (0.412)Intercept -0.367 (0.459)
Note: Robust standard errors reported, clustered by term.
Italicized variables are
statistically significant at the a=0.05 level. Federalism is the
omitted category. N=5675.
Beginning with the primary variable of interest, Public Mood
(Quar-terly), we find support for Friedman's basic claim. The
coefficient isstatistically significant and positively signed,
indicating that the moreliberal the public mood, the higher the
likelihood of a liberal deci-sion.
But how much higher? Keeping in mind that the Court usuallytakes
cases to reverse, the predicted probability of a liberal decisionis
.5946 when the Justices review a conservative lower court
decision
41and the public mood is very conservative. If the public mood
is veryliberal, the probability jumps to .71 . Alternatively, if
the Court re-views a liberal lower court decision when the public
is very conserva-tive, the probability that it will affirm (i.e.,
reach a liberal decision) isjust .33,49 but it increases to .4650
when the public is very liberal. Fig-ure 3 shows the predicted
probabilities in between these extremes,along with the 95%
confidence intervals.
45 See THE SUPREME COURT DATABASE, supra note 22.46 The 95%
confidence interval is [.54, .63].47 All other variables are set at
their mean or mode.48 The 95% confidence interval is [.66, .75].49
The 95% confidence interval is [.30, .37].50 The 95% confidence
interval is [.41, .52].
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FIGURE 4. PREDICTED PROBABILITY OF A LIBERAL DECISION IN A
CIVILLIBERTIES CASE AS THE PUBLIC MOOD MOVES FROM VERY
CONSERVATIVE TO VERY LIBERAL
Conservative Lower Court Decision
0C
80n
0
5-V
20~
50 55 60 65 70 - - 75Public Mood (Most Conservative to Most
Liberal) Public Mood (Most Conservative to Most Liberal)
Note: This figure is based on the model in Table 2. The black
lines indicate thepredicted probabilities in civil liberties cases
and the gray lines shows 95% confidenceintervals. To generate these
quantities of interest, we used S-Post. Civil Liberties is set
at
1. All other variables are set at their means (Ideology of the
Supreme Court, Ideology of thePresident, Ideology of the House,
Ideology of the Senate) or at their mode, which is 0 (U.S. Lib-eral
Party, U.S. Conservative Party, Economics, judicial Power).
Whether the difference in the predicted probabilities displayed
inFigure 3 is large or small is a question readers must answer for
them-selves. For what it's worth, we think they are large-actually
quitelarge-given that we control for many other variables that have
anappreciable effect on the direction of the Court's decisions.
The ideology of the Court, as represented in our model by
theideal point of the median Justice, provides an example. Table 3
tellsus that the effect is statistically significant, such that the
more conser-vative the median, the less likely a liberal decision,
and Figure 4 re-veals that the effect is quite dramatic. All else
being equal, the likeli-hood of the Court reversing a conservative
lower court decision (i.e.,reaching a liberal decision) when the
median Justice is very liberal is
-.7-
2
~ 6-
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a high .78.5' The likelihood plummets to .55 when the median is
veryconservative."
FIGURE 5. PREDICTED PROBABILITY OF A LIBERAL DECISION IN A
CIVILLIBERTIES CASE AS THE MEDLANJUSTICE MOVES FROM MOST
CONSERVATIVE TO MOST LIBERAL
Iaca
CL
0-
.8-
.6-
.5--1 -.5 .5
Ideology of the Median Justice (Most Uberal to Most
Conservative)
Note: This figure is based on the model in Table 2. The black
line indicates the predicted
probabilities in civil liberties cases and the gray line shows
95% confidence intervals. To
generate these quantities of interest, we used S-Post. Civil
Liberties is set at I and the Direction ofthe Lower Court Decision
is conservative. All other variables are set at their means (Public
Mood,
Ideology of the Supreme Cburt, Ideology of the President,
Ideology of the House, Ideology of the Senate) or at
their mode, which is 0 (U.S. Liberal Party, U.S. Conservative
Party, Economics, judicial Power).
This finding is not especially surprising. On most realist
theoriesof judging-especially judging on the Supreme Court-the
Justices'ideology affects their decisions. What is surprising is
that even aftertaking into account ideology, Public Mood continues
to be a statisti-cally significant and seemingly non-trivial
predictor of outcomes (seeTable 3 and Figure 4).
51 The 95% confidence interval is [0.75, 0.81].52 The 95%
confidence interval is [0.53, 0.58].
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IV. DISCUSSION
No doubt, our results should encourage Professor Friedman
andothers who believe that "the Court and the public will come into
basicalliance with each other.",53 At the least, our results
indicate that anassociation exists between the public's mood and
the Court's deci-sions.
Whether that association is something more-whether publicopinion
"influences" the Court, as the subtitle of Professor Fried-man's
book asserts-we cannot say. This is so for two reasons.
First,despite our efforts to control for the more obvious
determinants ofthe Court's decisions, our statistical model
undoubtedly misses someimportant variables. One indication of
under-specification comesfrom our own model. When we reestimated
it, retaining the main ef-fects of Public Mood (Quarterly) and the
issue area dummies but inter-acting Mood with the issues, we found
that public opinion was not agood predictor of the outcome in
Judicial Power cases. Because liti-gation in this area tends to fly
under the public's radar screen, the(non-)result implies the need
to control for the importance of eachcase. 4 Future research could
take this step by deploying any numberof measures of salience,
including the Epstein-Segal "New York Times"
-556approach, the number of participating amici, or even future
cita-tions to the opinion.
A second reason we are unwilling to make the leap from
associa-tion to causality is we have neither posited nor tested a
mechanismfor the effect of public opinion on the Court. Certainly,
Professor
53 FRIEDMAN, supra note 1, at 15.54 But see Giles, Blackstone
& Vining supra note 8, at 15 (finding that "the effects of
public
opinion on liberalism appear to be consistently less in salient
cases" because "case sali-ence may actually intensify the operation
of [the Justices' own ideological] preferences").
55 Lee Epstein & Jeffrey A. Segal, Measuring Issue Salience,
44 AM. J. Pot. SCI. 66, 72 (2000)(measuring issue salience by
whether the New York Times carried a front page story aboutthe
case).
56 FORREST MALT/MAN, JAMES F. SPRIGGS II & PAUL J. WAHLBECK,
CRAFTING LAW ON THESUPREME COURT: THE COLLEGIAL GAME 46 (2000)
(measuring political salience by "de-termin[ing] whether a case had
more amici filings than the average case heard during aterm").
57 See, e.g., James H. Fowler et al., Network Analysis and the
Law: Measuring the Legal Importanceof Precedents at the U.S.
Supreme Court, 15 PoL. ANALYSIS 324, 326 (2007) ("It ... seems
rea-sonable to determine how relevant a particular opinion is by
considering how it is em-bedded in the broader network of opinions
compromising the law."); Lee Epstein, Wil-liam M. Landes &
Richard A. Posner, Why (and When) judges Dissent: A Theoretical
andEmpirical Analysis 14 (John M. Olin Law & Econ., Working
Paper No. 510, 2d series,2010), available at
http://papers.ssrn.com/sol3/papers.cfm?abstractid=1542834 ("Weproxy
importance by the number of Supreme Court and court of appeals
citations to theopinion.").
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Friedman and others could be right: the public has a direct
influ-ence on the Court because the Justices are concerned about
their le-gitimacy in the short and long-terms. But it is equally
plausible, asFlemming and Wood explain, that the Justices are
simply "social be-ings confronted with the plethora of stimuli
emanating from Ameri-can culture, media and politics.""s In other
words, the same thingsthat influence public opinion may influence
the Justices, who are, af-ter all, members of the public too.
Until we can behaviorally distinguish and assess these and
othermechanisms, statistical confirmation of Professor Friedman's
causalstory must wait yet another day. What we can say, and what
our re-sults suggest, is that his account is not as implausible as
some of thepolitical science literature suggests.
58 Flemming & Wood, supra note 10, at 471.
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